Wheel alignment is a process of adjusting the angles of wheels on a vehicle so that they are generally perpendicular to the ground and parallel to one another. The purpose of such adjustments is to attain maximum tire life, as well as to ensure that the vehicle tracks straight when driving along a straight and level road.
In order to adjust the wheel angles to achieve proper wheel alignment, the actual wheel angles must first be measured, such that the requisite adjustments may then be calculated. Two particular angles that are utilized in wheel alignment methods are commonly referred to as “camber” and “toe.” Camber, which is typically measured in degrees, is the angle of the wheel's deviation from a vertical plane. Therefore, camber is angle of the wheel that is seen when viewed from the front of the vehicle. If the top of the wheel is leaning out from the center of the car, the camber is positive; if it is leaning in toward to center of the car, then the camber is negative. Toe is the difference in distance between the front of two tires and the back of those tires. It is normally measured in fractions of an inch, and is usually set close to zero, meaning that the wheels are substantially parallel to one another. “Toe-in” means that the fronts of the tires are closer to each other than the rears; “toe-out” is the opposite situation.
Some types of wheel alignment procedures involve placing optical instrumentation on each of a vehicle's four wheels. The instrumentation may be assembled together in a “head” that is clamped to each of the wheels. A head may include a transmitting device such as an LED emitter, and a receiving device such as a photosensor. During an alignment procedure, the receiving device of each head “looks” at the transmitted light from two heads of the two adjacent wheels. The optical “box” that is formed around the four wheels by the transmitting devices may thus be sensed by the four receiving devices as the wheels are rotated, and the various angle wheels may thereby be calculated. However, such procedures involve certain inherent measurement inaccuracies and can therefore result in alignment errors. For example, if a head is clamped to a wheel incorrectly, inaccurate measurements may result.
Other alignment systems have utilized non-optical sensors for measuring alignment angles, such as magneto resistive sensors on pendulums, electrolytic vials and other pendulum type devices. These types of sensors may not be as susceptible to wobble and other errors that optical sensors may encounter. However, magneto resistive and pendulum based elements are susceptible to breakage and accuracy problems caused by mechanical shock. An additional drawback is that these types of sensors can often be bulky and difficult to handle, and are relatively expensive.
What is needed is a wheel alignment method that utilizes a lighter, less expensive sensor on the measurement heads. What is further needed is a wheel alignment system whose measurement heads have improved robustness capable of withstanding increased mechanical shock without breaking or deviating in measurement accuracy.